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Rick Miley 06-09-2003 04:40 PM

June is Cooling System Month
Since everybody else is posting about their cooling system problems, I'll chime in with mine. Becuase of a faulty relay connection, I've had some experience with an inoperative aux fan in the 240D. I've noticed that when the fan isn't working, the coolant temp quickly runs up to 105 at any road speed. When the fan is working, however, the coolant stays right at 90.

I would have expected more ram air coming through that huge upright W123 grill at highway speeds, but apparently it needs help from the electric fan. Does anyone think the cooling system has a problem?

And no, I'm not ready to sell this car yet. :D

The Warden 06-09-2003 04:54 PM

On hot days with the a/c on, my water temp will start to rise. I shut the a/c off at 100 to prevent damage, although I'm sure that the cast-iron OM617 can handle it. This is with a non-operational auxiliary fan, and I also believe that my engine fan clutch is dead.

Have you ever heard the engine fan activate? If it's anything like the fan on my truck, the car will all of a sudden start doing its jet engine impression. In addition, the car might feel like it's losing some power, but I'm not sure on that. If you're not getting this, try spinning the fan with the engine not running...if the engine's cold, it should turn but with difficulty.

My guess would be that the engine fan clutch is dead but that the cooling system is otherwise happy. I'm sure it could stand to be flushed out, though...I know that I need to do that with mine. :)

Hope that helps some...good luck!

leathermang 06-09-2003 06:08 PM

Well, you are just having one thermal problem after another... bummer given where you live..
"engine fan clutch is dead " I second this probablilty.. and you might as well switch to the 9 bladder while you are in there..
Reminder... the fan clutch is supposed to be stored vertically,,,, and do not set it down on its front side...
If this does not really really help... it might be time to blast the inside of the block and flush...and clean or replace the radiator....and check the opening temp of the thermostat... and make sure you do not have any air bubbles...

But call me if you get really disgusted working on such an old car....:D

Old Deis 06-09-2003 06:52 PM

Two years ago in the sweltering NW heat (I think it got to 80 that week) I began to notice some high temps on the old 78 300D.
The cure was to remove the radiator and spray through the fins with degreasor and then water. Amazing how much stuff was in there. Can't do it in place very well with the AC condensor sitting right behind it.

slowmoe 06-09-2003 08:08 PM

One of the two aux fans on my 124 went this time last year. When I removed the fan for replacement, I noticed a ton of road junk caught between the fan motor and the AC condensor essentially restricting any airflow to the vents of the motor. I believe that this ultimately caused the failure.

Perhaps periodic cleaning of this vital area could save someone $131 and a few knuckle scrapes.

engatwork 06-09-2003 08:59 PM

I took my 240D up to Jackson on Sunday to take a look at an old 180. On the interstate, at 80 with the a/c on max and going up hills it would go to 100 dC or just slightly above. Shutting the air off and running heat on hi would drop it immediately. I am putting a new radiator and water pump in it over thne next day or so and will let ya'll know if that makes any difference. I did notice that the impeller on the water pump is slightly smaller than the new one. The 300D gets to 90 dC and stays there under the same conditions. I'll keep ya'll posted.

Rick Miley 06-10-2003 10:56 AM

No fan clutch on this baby.
It's got a solid metal hub. Greg, does yours have a clutch? I'm thinking that might be a nice addition, so the fan doesn't draw engine power when not needed. Imagine that - having some extra power on tap in a 240D! OTOH, this being sunny Florida, the clutch would be engaged most of the time anyway. :(

I'm not in fear of the engine overheating, now that the electric fan is working. And I have plans to change the coolant and clean the exterior of the radiator while I'm there. I was just hoping for some comment on the apparent lack of ram air effect.

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